add make_df_trans_probs to article.utils
add make_df_trans_probs to article.utils

- makes dataframe for calculating transition probabilities of song syllables
  from vak Dataset objects
  + assumes audio files are .cbin files since this is mainly being used for
    analysis of results from Bengalese Finch Song Repository dataset, which
    is all .cbin files
- also added date_from_cbin_filename helper function that is used by make_df_trans_probs

yardencsGitHub/tf_syllable_segmentation_annotation